This invention relates to the treatment of lignite containing ash-producing clay. In another of its aspects, this invention relates to methods for separating lignite from the more friable clay with which it is associated as mined. In another of its aspects this invention relates to the classification of mine-run lignite to provide a product suitable for use, a product suitable for use after further treatment, and a waste product for disposal.
ln some areas of this country, large reserves of lignite have been found that would support mine-mouth, electric generating plants. Large scale open-pit mining would be considered the proper method for using these reserves; however, in some areas of the reserves, where seams are thin or discontinuous, the avoidance of clay contamination of the lignite would be difficult when using the large-scale excavation equipment necessary for economical development of the reserves.
Extraneous clay material is classified as ash in a power plant assay and serves to reduce both the heating value and market value per ton of the mined lignite. Enhancement of the market value of high ash, low-BTU lignite can be accomplished through beneficiation operations which reduce the clay content. The concept of this invention provides a method by which mine-run lignite of relatively high clay contamination can be treated to reduce the ash content and thereby produce a more salable and useful product.
The invention is based on a process which selectively shatters friable, high-ash containing lignite along clay seams thereby exposing and breaking up the clay which is more friable than the carbonaceous lignite to produce clay particles generally smaller than the lignite particles. This allows further treatment for separation of the lignite and clay to upgrade the percentage of lignite in the mixture of materials.
It is therefore an object of this invention to provide a method for reducing the clay content of a heterogeneous mixture of mine-run lignite containing clay. It is another object of this invention to provide a combination of treatments to separate clay from lignite containing clay. It is still another object of this invention to provide a method for treating lignite particles containing clay seams and/or clay attached to the lignite surfaces preferentially to shatter the particles along the more friable clay portions of the particle.
Other aspects, objects and the various advantages of this invention will become apparent upon reading the specification and the appended claims.